Months that have 31 days are: January, March, May, July, August, October, December.

why does JUNE only have 30 days? When the Julian calendar was instituted by Julius Caesar, it was defined that the months would alternate between 30 and 31 days in order to comply with the solar year. However, this still didnt match to the solar year, so one of the months would have to have only 29 days.

In respect to this, why are there 30 days in a month?

The ancient Romans, like ancient civilizations before them, based their concept of the month on the Moon. Julius Caesar modified the Roman calendar in 46 B.C. to make each month have either 30 or 31 days, with the exception of Februarius, which had 29 days and gained an extra day every fourth year.

What months only have 28 days?

The answer is 1, February but that only applies when its not a leap year when February has 29 days. Remembering how many days each month has is quite a pain, but there is always one month you can remember; February is the only month that has only 28 (or 29) days.